Kiss Ligands and Receptors Flashcards
What do ligands bind to?
ligands bind to the receptor
What are the 4 different ways to send signals?
- contact dependent
2.paracine - synaptic
- endocrine
How does contact dependence work?
How does paracrine signaling work?
contact dependence= one cell can physically interact with another cell
paracrine-cell can release signal that can go to surrounding cells
How does synaptic signaling work?
How does endocrine signaling work?
-synaptic signaling (nerve cells) send signal from axon to dendrite
-encodrine=signal goes through the blood (hormone signaling)
What are the characterisitics of a cell surface receptor (what does it have on it)
it has a cells surface receptor protein on plasmam membrane and a hydrophillic sgnal molecule (which is water soluble, polar charged which cannot go through membrane)
What are the chracteristics of intracellular receptors?
-has a carrier protein which brings a small hydrophobic signal molecule which goes through the plasma membrane and into the intracellular receptor protein (inside cell)
What are the 4 different ways in which cells react to different signals?
1.help cell survive
2.grow and divide
3.differentiate
4.die
What does the ach signal molecule bind to?
What is it composed of (what groups)?
-binds to g-protein coupled receptor which can affect multple things in various cells
-composed of a choline and acetyl group
What are the 3 functions that ACH can have on the body?
-act on a pacemaker cell to decrease rate of firing
-act on salivary gland to secrete (helps you drool)
-act on skeletal muscle for contraction
what are the 3 different kinds of receptors?
-ion channel coupled receptors
-g protein coupled receptors
-enzyme coupled receptors
How does an ion channel coupled receptor work?
-it brings ions into cells using a special transporter since ions are charged, goes against the gradient so ATP is used
How does a g protein coupled receptor work, what does it bind and what does it recruit when bound?
how many TM domains does it have?
-7 TM domain G protein is activated by binding a signaling molecule
-when its bound to signal molecule it is activated and recruits 3 subunits alpha, beta and gamma
How do enzyme coupled receptors work?
What does the intracellular part contain, what does it commence?
What happens when phosphorylation occurs?
-there are 2 receptors that when a ligand is bound they homodimerize/heterodimerize depending on subunits
-intracellular part has enymatic activity (often tyrosine kinase domain), which comes in contact with homodimer/heterodimer and commences trans phosphorlyation
-after phosphor. downstream signaling event can occur
How does signaling by phosphorlyation work?
What are the components involved with it?
protein kinase changes ATP to ADP (adds a phosphate) and turns on the signal
-then protein phosphatase removes a phoshphate and turns off the signal
How does signaling by GTP binding work?
What are the components involved, how does it tunr off/on
-a signal coming in converts GDP to GTP (GTP binding), GEF activates GTP which turns on signal, allows it to leave
-GTP hydrolysis gets rid of a phosphate (GAP does this) and turns off the signal in GDP bound form
What occurs in performed signaling complex on a scaffold protein, how is the signal activated?
What occurs after the signal is activated?
There is an inactive receptor with 3 inactive scaffold proteins, once a signal molecule comes in the receptor becomes active
-once receptor is active and recruits the scaffoling proteins, the scaffold proteins are all activated leading to downstream signaling
how does assembly of signaling complex on an activated receptor work?
how is it activated and what happens after activation?
-there is an inactive receptor and inactive intracellular signaling proteins,
-but once a signal molecule binds, the intracellular signaling proteins are activated and send a downstream signal
how does assembly of signaling complex on phosphoinositde docking sites work?
how is it activated and what happens after activation?
There is an inactive receptor, specific phospholipid molecules and inactive intracellular proteins
-once a signal molecule binds on the receptor activating it, the phoshpholipid molecules will become hyperphosphorlyated and activate the intracellular signaling proteins causing downstream signals since they are ligands for cytosolic proteins
What does the PTB, SH2, SH3, and PH domain do in terms of binding?
PTB domain- binds to NPXY phoshphotyrosine
-SH2 domain= binds to phosphorlyated residue
-SH3=binds to proline rich regions
PH domain= binds phosphatadyl inositol (PI) 4,5 and different proteins
How does signal integration work?
-Extracellular signals A and B activate different intracellular signaling pathways, each of which leads to the phosphorylation of protein Y but at different sites on the protein.
-Protein Y is activated only when both of these sites are phosphorylated, and therefore it becomes active only when signals A and B are simultaneously present.
What is allostery?
What happens when more ligands are needed?
some proteins require function of mulitple proteins to lead to allostery, which tighyl regulates proteins
-For example the more ligands required to bind the longer it takes for activity to occur
What is positive vs negative feedback?
-positve feedback=when you have a stimulus which leads to more product being produced
-negative feedback=when you have stimulus which causes less product to be produced (inhitbit production)
When are the alpha beta gamma subunit activated?
-What happens when the subunits are activated?
-they are activated after the GPCR (g protein coupled receptor) complex binds to the signal molecule which changes the intraceullar domain recruiting alpha, beta, gamma
-when subunits are activated they lose GDP and then GTP can bind to the alpha subunit
What happens when GTP is bound to alphs subunit?
-the beta and gamma subunit detach together from the alpha subunit and go to mediate signaling events
How do we control signaling events with cyclic AMP?
What is cyclic AMP made of?
what are the steps/components involved with making CAMP?
cyclic AMP is made up of phosphate bound to 2 hydroxys on ribose sugar via ATP and this forms a loop via the phosphate
-enzyme to make cyclic amp is andenyla cyclase which removes 2 phosphates and allows the phophates to bidn to the sugar again
How do we destroy cAMP?
how do we create more cAMP?
What do we do if we need more signaling?
-via a phosphodiesterase enzyme
-we temporariliy activate adenylyl cuclase and then create cAMP, then generate signaling events then terminate cAMP
-generate more cAMP
What is the mechanism of cyclic AMP to bind regulatory subunits?
-cAMP works via binding to the ezyme cAMP dependent protein kinase (PKA)
What do PKA subunits bind to/do?
How does a signaling event start?
-they bind to cAMP, it can bind 4 molecules of cAMP so that the regulatory subunits of the catalytic subunits are active
-signaling event starts when PKA phosphorylates its target
What are the 4 steps that lead to transcription of the desired genes we want using GPCR and cAMP?
(Steps 1 and 2)
-What is activated and what does adenyly cyclase generate?
-what does cAMP bind to?
- activated GPCR and alpha subunit is actiavted by GTP and connected to adenylyl cyclase to generate cAMP
-2.cyclic AMP binds to regulatory subunits of PKA
What are the 4 steps that lead to transcription of the desired genes we want using GPCR and cAMP?
(Steps 3 and 4)
3. what is activated and phoshphor.
4.what does this result in?
Once cAMp binds PKA, PKA releases the 4 activated
subunits (catalytic domains) to go into the nucleus and phosphorylate CREB (cyclic amp activated
4.PKA phosphorylating CREB results in promotion of transcription of genes that we want
What is PI 4,5 bisphosphate composed of?
What do you do if you want to get rid of a protein?
-composed of a diacyclglycerol (ester linked aceyl chains bound to glycerol backbone)
and a phosphoinositol
-you cleave off one of the phosphates
What does phosphlipace C beta do?
What does each molecule activate/release?
-it cuts PI 4,5 bisphosphate into 2 segments at the diacylglyerol portion, leaving a diacylgylcerol whihc actiavtes protein kinase C and
-an inositol 1,4,5 triphosphate (a good 2nd messenger) which releases Ca2+ from the ER
How is phospholipase C beta recruited in order to activate protein kinase C
-GPCR is actiavted by signaling molecule, it then actiavtes the alpha subunit which binds GTP, activaitng the beta an gamma subunit further to recruit phosphlipase C beta
-this cleaves off the inositol from PI4,5 bisphohsphate which cleaves, cutting off IP3 and leaving diglyercol which both activate protein kinase C
What is the signaling cascade that leads to dilation in BP control?
-what is the ligand that activates GPCR, what does this lead to release of?
What does thi activate, what does this lead to production of?
What is the target of the nitric oxide?
-Acetylcholine is the ligand that activates G protein coupled receptor, which leads to release
of IP3 which leads to calcium release which leads to activation of NOS,
-which leads to the production of nitric oxide which travels through the blood (soluble in blood), finds target tissue (often SM cells of arteries) and leads to relaxation (dilation) and this control the BP
How do we turn off GPCR pathway?
What is the kinase called?
what does the kinase do/cause?
ligand binds to G protein activating GPCR, now GERK comes
- GPCR kinase (GERK) phosphorylates at a number of sites that interact w alpha subunit when recruiting alpha beta gamma subunit this is the part that undergoes a conformational change when the messenger (ligand) is bound
what does arrestin do?
- Now a diff protein binds (arrestin) to ligand and blocks the proper activation or binding of alpha subunit and the signal transduction cascade is blocked (arrestin protein)
- acute way of regulating G protein coupled receptor
What happens when a receptor tyrosine kinase (RTK) encounters a signal protein?
What does this generate?
What do these proteins signal?
-the 2 monomers do trans autophosphor. which activates RTK
-this generates binding sites for signal proteins
-these activated signaling proteins relay downstream signal
What does EGF do when it encounters an inactive monomer?
What causes an active dimer?
-EGF promotes homodimerization of 2 molecules of EGF receptor
-EGF binds receptor and forms dimer
-transphosphor of the receiver and activator causes dimerization
How does RTK activate RAS (part 1)
-how does this start?
What binds to phosphotyrosine, via what domain, what does it bind to?
ligand binds to the receptor, autophosphorylation occurs
* trans-phosphorylation occurs (one monomer phosphorylates the other and vice versa)
* protien called Grb2 is binding to phosphotyrosine via SH2 domain and binds to proline rich domain via SH3 domain and that
recruits the second protein Sos
How does RTK activate RAS (part 2)
What does SOS have, and what does this lead to?
How does cancer result?
- SOS has a GEF domain which promotes the binding of GTP and removal of GDP and now Ras has been activated, downstream signalling is activated
-cancers result from mutation of Ras or Ras signalling pathways - Connect receptor tyrosine kinase with the small mol GTP binding protein bc one of these interacting adaptor proteins is a GEF so it activates the Ras
What is FRET and what does it do?
What do we attach the fluorescent protein to?
FRET: fluorescence resonance energy transform is used to detect proximity of something
* basically: we SHine light on smthg at a certain wavelength and a higher wavelength comes off
(lower energy)
* shine blue light on something and then green light comes off, yellow light produces red light
* Attach fluorescent protein to Ras then activate te protein by shining low light thne it gives off another
wavelength light
What wavelengths do the 2 fluorphores activate in activation of RAS revealed by FRET?
How do we kno is Ras is activated, what color do we see?
- GTP bound to red fluorescent dye, red activated by light of another wavelength
- We have 2 flourophoeres, 476 activating 528nm, then 528 activating 617, combine the 2 tg adn we
detect the emission from second one and know the 2 mol are close in proximity - EGF added we know Ras is activated and we see lots of red spectrum
How does Rheb get activated in to create the MTOR complex 1 using growth factors?
How does RTK get activated to produce Rheb GAP, what are the subunits involved?
-when growth factor bind to RTK (receptor tyrosine kinase), dimerization and autophosphorylation occurs, which activates 2 separat signaling cascades Akt and Erk (MAPK) that interact with a small molecule GTP binding protein TSC (Rheb GAP) to inihibit GAP
-this allows GTP to bind to Rheb
-this activates MTOR
How does Gator 2 inhibit Gator 1 (Rag GAP) in the MTOR complex?
What side of the complex is it apart of, how does the inhibition occur (what are the steps)
(part 1)
In the case of Rag, the GAP is a protein complex called Gator1, which is anchored on the lysosome and is regulated by a series of inhibitory interactions:
-cytosolic amino acids bind receptor proteins, thereby removing their inhibitory effect on Gator2, which is then free to inhibit the GAP activity of Gator1—resulting in Rag activation and binding to mTORC1
On the Rag side of the MTOR complex what is the Rag GEF called that is needde for interaction of rag with lysosome?
The interaction of Rag with the lysosome depends on a large protein complex, the Ragulator, that serves as an activating GEF for Rag; this GEF activity is stimulated by amino acids in the lysosome, further promoting mTORC1 activation.
-it basically activates Rag
What are the 3 main pathways that we need to know for RTK and GPCR activity?
1.PKA
2.PKC
3. MAPK (also known as Erk, involved in Rheb activity of MTOR side)
What are the different sterioid hormones?
Name all 6
1.cortisol=influences metabolism
2.estradiol=sex hormone
3.testosterone=sex hormone
4.vitamin D3=regulates ca2+ metabolism
5.thryoxine=thryoid hormone that increases metabolism
6.retionic acid=play role in vertebrae development
What are the characteristics of steroid hormones?
-Where do they bind and when (after crossing what)
-what happens once they are bound
-they are amphipathic, but a bit more hydrophobic so they can bind to receptor not on the PM
-after crossing the PM they find and bind to the steroid receptor
-once thery are bound they travel into the nucleus where they act as a TF to promote or inhibit transcription
